如果向量包含字符串值，并且它们之间用特殊字符分隔（该特殊字符可以是任何字符，也不一定是特殊字符），并且我们只想提取该特殊字符之前存在的值，则可以使用gsub函数。例如，如果我们的向量x包含“ UT / YT”，“ IST / IT”，“ PST / PT”，则gsub可以帮助我们提取UT，IST，PST。
x1<-c("Alabama/Alaska", "American Samoa/Arizona", "Arkansas/California", "Colorado/Connecticut", "Delaware/District of Columbia/Florida", "Georgia/Guam", "Hawaii/Idaho", "Illinois/Indiana", "Iowa/Kansas", "Kentucky/Louisiana", "Maine/Maryland", "Massachusetts/Michigan", "Minnesota/Minor Outlying Islands", "Mississippi/Missouri", "Montana/Nebraska", "Nevada/New Hampshire", "New Jersey/New Mexico", "New York/North Carolina", "North Dakota/Northern Mariana Islands", "Ohio/Oklahoma", "Oregon/Pennsylvania", "Puerto Rico/Rhode Island", "South Carolina/South Dakota", "Tennessee/Texas", "U.S. Virgin Islands/Utah", "Vermont/Virginia", "Washington/West Virginia", "Wisconsin/Wyoming")输出结果
x1 [1] "Alabama/Alaska" [2] "American Samoa/Arizona" [3] "Arkansas/California" [4] "Colorado/Connecticut" [5] "Delaware/District of Columbia/Florida" [6] "Georgia/Guam" [7] "Hawaii/Idaho" [8] "Illinois/Indiana" [9] "Iowa/Kansas" [10] "Kentucky/Louisiana" [11] "Maine/Maryland" [12] "Massachusetts/Michigan" [13] "Minnesota/Minor Outlying Islands" [14] "Mississippi/Missouri" [15] "Montana/Nebraska" [16] "Nevada/New Hampshire" [17] "New Jersey/New Mexico" [18] "New York/North Carolina" [19] "North Dakota/Northern Mariana Islands" [20] "Ohio/Oklahoma" [21] "Oregon/Pennsylvania" [22] "Puerto Rico/Rhode Island" [23] "South Carolina/South Dakota" [24] "Tennessee/Texas" [25] "U.S. Virgin Islands/Utah" [26] "Vermont/Virginia" [27] "Washington/West Virginia" [28] "Wisconsin/Wyoming"
gsub("/.*$","",x1)输出结果
[1] "Alabama" "American Samoa" "Arkansas" [4] "Colorado" "Delaware" "Georgia" [7] "Hawaii" "Illinois" "Iowa" [10] "Kentucky" "Maine" "Massachusetts" [13] "Minnesota" "Mississippi" "Montana" [16] "Nevada" "New Jersey" "New York" [19] "North Dakota" "Ohio" "Oregon" [22] "Puerto Rico" "South Carolina" "Tennessee" [25] "U.S. Virgin Islands" "Vermont" "Washington" [28] "Wisconsin"
x2<-c("AK/AL","AR/AS","AZ/CA","CO/CT","DC/DE","FL/GA","GU/HI","IA/ID","IL/IN","KS/KY","LA/MA","MD/ME","MI/MN","MO/MP","MS/MT","NC/ND", "NE/NH","NJ/NM","NV/NY","OH/OK","OR/PA","PR/RI","SC/SD","TN/TX", "UM/UT","VA/VI","VT/WA","WI/WV","WY")输出结果
x2 [1] "AK/AL" "AR/AS" "AZ/CA" "CO/CT" "DC/DE" "FL/GA" "GU/HI" "IA/ID" "IL/IN" [10] "KS/KY" "LA/MA" "MD/ME" "MI/MN" "MO/MP" "MS/MT" "NC/ND" "NE/NH" "NJ/NM" [19] "NV/NY" "OH/OK" "OR/PA" "PR/RI" "SC/SD" "TN/TX" "UM/UT" "VA/VI" "VT/WA" [28] "WI/WV" "WY"
gsub("/.*$","",x2)输出结果
[1] "AK" "AR" "AZ" "CO" "DC" "FL" "GU" "IA" "IL" "KS" "LA" "MD" "MI" "MO" "MS" [16] "NC" "NE" "NJ" "NV" "OH" "OR" "PR" "SC" "TN" "UM" "VA" "VT" "WI" "WY"
x3<-c("Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria/Azerbaijan","The Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bhutan Bolivia Bosnia and Herzegovina Botswana Brazil Brunei Bulgaria Burkina Faso/Burundi","Cabo Verde Cambodia Cameroon Canada Central African Republic Chad Chile China Colombia Comoros Costa Rica Côte d’Ivoire Croatia Cuba Cyprus/Czech Republic","Denmark Djibouti Dominica/Dominican Republic","Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Eswatini/Ethiopia")输出结果
x3 [1] "Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria/Azerbaijan" [2] "The Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bhutan Bolivia Bosnia and Herzegovina Botswana Brazil Brunei Bulgaria Burkina Faso/Burundi" [3] "Cabo Verde Cambodia Cameroon Canada Central African Republic Chad Chile China Colombia Comoros Costa Rica Côte d’Ivoire Croatia Cuba Cyprus/Czech Republic" [4] "Denmark Djibouti Dominica/Dominican Republic" [5] "Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Eswatini/Ethiopia"
gsub("/.*$","",x3)输出结果
[1] "Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria" [2] "The Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bhutan Bolivia Bosnia and Herzegovina Botswana Brazil Brunei Bulgaria Burkina Faso" [3] "Cabo Verde Cambodia Cameroon Canada Central African Republic Chad Chile China Colombia Comoros Costa Rica Côte d’Ivoire Croatia Cuba Cyprus" [4] "Denmark Djibouti Dominica" [5] "Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Eswatini"